Date

Study of the reaction anti-p p ---> Anti-lambda Lambda below 6-MeV excess energy

Barnes, P.D. ; Birien, P. ; Breunlich, W.H. ; et al.
Phys.Lett.B 331 (1994) 203-210, 1994.
Inspire Record 382628 DOI 10.17182/hepdata.28665

The reaction p p → Λ Λ → p π + pπ − is studied in the experiment PS185 at the CERN Low Energy Antiproton Ring (LEAR). A precise measurement of the excitation function in the immediate threshold region below 6 MeV excess energy was achieved. The total cross section shows an unexpected behaviour around 1 MeV excess energy.

2 data tables

The values are calculated using M(p)=M(pbar) = 938.27231 Mev and M(lambda)=M(lambdabar) = 1115.63 MeV.

D(SIG)/D(OMEGA) as a function of COS(THETA(RF=CM)) for the nine intervals of the excess energy. Excess energy is SQRT(S)-M(lambda)-M(lambdabar).


Mass dependence of pi0 production in heavy ion collisions at 1-A/GeV

Schwalb, O. ; Pfeiffer, M. ; Berg, F.-D. ; et al.
Phys.Lett.B 321 (1994) 20-25, 1994.
Inspire Record 376130 DOI 10.17182/hepdata.28781

The production of neutral pions has been studied in the reactions 40 Ar + nat Ca , 86 Kr + nat Zr and 197 Au + 197 Au at 1 A GeV. For high energy pions emitted from the heavier systems a steeper than linear rise of the pion multiplicity with the centrality of the reaction is observed, indicating a pion production process other than binary nucleon-nucleon collisions. At low transverse momenta an enhancement of the π 0 -multiplicity increasing with the mass of the collision system is found. Systematic discrepancies between the experimental results and recent BUU, QMD and Cascade calculations are discussed.

6 data tables

No description provided.

RESULTS OF AN EXTRAPOLATION TO THE FULL SOLID ANGLE TAKING THE EXPERIMENTALTEMPERATURES INTO ACCOUNT.

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Measurement of the double spin asymmetry A-LL for inclusive multi gamma pair production with 200-GeV/c polarized proton beam and polarized proton target

The FNAL E581/704 collaboration Adams, D.L. ; Akchurin, N. ; Belikov, N.I. ; et al.
Phys.Lett.B 336 (1994) 269-274, 1994.
Inspire Record 378852 DOI 10.17182/hepdata.28569

The invariant double-differential cross section, E 1 E 2 d 6 σ / d p 3 1 d p 3 2 , and the double-spin asymmetry, A LL , for inclusive multi-γ pair production in which γ-rays came from neutral mesons were measured with a 200 GeV / c longitudinally-polarized proton beam and a longitudinally-polarized proton target. Most of the multi-γ pairs comes from two-jet type events which are sensitive to partonic interaction. The A LL values were found to be consistent with zero. The invariant double-differential cross section for inclusive π 0 π 0 production was also measured. These measured cross sections are consistent with LUND Monte Carlo simulations. Using the LUND Monte Carlo simulation package with the Carlitz-Kaur model of spin dependent distribution functions of valence quarks, the A LL values have been compared with theoretical predictions of gluon polarization, ΔG / G . The results put restrictions on the size of ΔG / G in the region of 0.05 ⪅ x ⪅ 0.35.

3 data tables

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Phi and omega meson production in anti-n p annihilation and the OZI rule

The OBELIX collaboration Ableev, V.G. ; Agnello, M. ; Balestra, F. ; et al.
Phys.Lett.B 334 (1994) 237-243, 1994.
Inspire Record 383126 DOI 10.17182/hepdata.28740

The φπ + /ωπ + ratio from n¯p annihilations on a liquid hydrogen target, for n¯ momenta between 64 and 297 MeV/ c , was measured using the OBELIX spectrometer at LEAR. The ratio R(ϕπ/ωπ)=σ(n¯p→ϕπ+)/σ(n¯p→ωπ+) turned out 0.110±0.015 stat ±0.006 syst . Implications of this result on the OZI rule are discussed.

1 data table

Assumes branching ratios of (49.1 +- 0.8)% for phi --> K+ K- and (88.8 +- 0.6)% for omega --> pi+ pi- pi0.


A Study of the transverse polarization of Lambda0 and Anti-lambda0 hyperons produced in pi- Cu interactions at 230-GeV/c

The ACCMOR collaboration Barlag, S. ; Becker, H. ; Bożek, A. ; et al.
Phys.Lett.B 325 (1994) 531-535, 1994.
Inspire Record 377671 DOI 10.17182/hepdata.28729

We study the polarization with respect to the normal to the production plane for a very clean sample of 27217 Λ 0 / Λ 0 hyperons produced in 230 GeV/ c π −  Cu interactions. In general we find P(Λ 0 ) ≈ P( Λ 0 ap; 0 except for x F > 0, p T > 1GeV/ c where P ( Λ 0 ) = −0.28±0.09(stat.)±0.02(syst.).

4 data tables

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Radiative decay of the Delta resonance: Analyzing powers for pi- p (polarized) ---> gamma n

Stasko, J.C. ; Bassalleck, B. ; Booth, E.C. ; et al.
Phys.Rev.Lett. 72 (1994) 973-976, 1994.
Inspire Record 376202 DOI 10.17182/hepdata.19677

The polarized target asymmetry AN for π−p→→γn has been measured by coincident detection of the γ and the neutron at several angles across the Δ resonace energy region. A high-resolution NaI γ spectrometer together with good time-of-flight information for the neutron resulted in excellent separation of this radiative capture reaction from the much higher cross-section charge exchange reaction π−p→→π0n. Statistical uncertainties are ΔAN=0.02-0.04, representing a significant improvement over previous results. The new data are discussed in the context of recent theoretical models.

1 data table

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Neutron halo in heavy nuclei from anti-proton absorption

Lubinski, P. ; Jastrzebski, J. ; Grochulska, A. ; et al.
Phys.Rev.Lett. 73 (1994) 3199-3202, 1994.
Inspire Record 384612 DOI 10.17182/hepdata.19678

A new method to study the nuclear periphery using antiproton annihilation was applied to nine isotopes with mass numbers between 58 and 238. The method makes use of the detection of the radioactive annihilation products one unit lower in mass number than the target. A clear neutron halo effect, strongly correlated with the neutron binding energy, was observed in some nuclei. The experimental results are in qualitative agreement with calculations of proton and neutron densities at the nuclear periphery based on either a simple asymptotic density model or a more complex Hartree-Fock approach.

3 data tables

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A(FRAGT)=A(TARGET)-1.


Nuclear dependence of neutral D meson production by 800-GeV/c protons

The E789 collaboration Leitch, M.J. ; Boissevain, J. ; Carey, T.A. ; et al.
Phys.Rev.Lett. 72 (1994) 2542-2545, 1994.
Inspire Record 371874 DOI 10.17182/hepdata.19694

The nuclear dependence for 800 GeV/c proton production of neutron D mesons has been measured near xF=0 in Experiment 789 at Fermilab. D mesons from beryllium and gold targets were detected with a pair spectrometer and a silicon vertex detector via their decay D→Kπ. No nuclear dependence is found, with a measured α=1.02±0.03±0.02. The measured differential cross section, dσ/dxF, for neutral-D-meson production at 〈xF〉=0.031 is 58±3±7 μb/nucleon. The integrated cross section obtained by extrapolation of the measured cross section to all xF is 17.7±0.9±3.4 μb/nucleon and is consistent with previous measurements.

8 data tables
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Spin correlation measurements for p (polarized) + p (polarized) elastic scattering at 497.5-MeV

Hoffmann, G.W. ; Barlett, M.L. ; Kielhorn, W. ; et al.
Phys.Rev.C 49 (1994) 630-632, 1994.
Inspire Record 383760 DOI 10.17182/hepdata.25964

The spin correlation parameter A00NN for 497.5 MeV proton + proton elastic scattering was determined over the center-of-momentum scattering angle region 23.1°–64.9 °. The new A00NN extend to more forward angles than existing A00NN and have significantly smaller statistical errors (±0.01–0.04). The A00NN are qualitatively described by recent phase shift analyses, but a quantitative shape and normalization discrepancy remains in the forward angle region. These new data provide important constraints for nucleon-nucleon spin-dependent amplitudes at forward angles which are used in theoretical models of nucleon-nucleus scattering.

1 data table

Errors include statistical and systematic uncertainties.


Centrality dependence of longitudinal and transverse baryon distributions in ultrarelativistic nuclear collisions

The E814 collaboration Barrette, J. ; Bellwied, R. ; Braun-Munzinger, P. ; et al.
Phys.Rev.C 50 (1994) 3047-3059, 1994.
Inspire Record 385496 DOI 10.17182/hepdata.25982

Inclusive double differential multiplicities d2N/dy dpt and related quantities have been measured for protons and deuterons produced in 14.6A GeV/c Si+Al and Si+Pb collisions using the E814 forward spectrometer at the AGS at BNL. Collision ‘‘centrality’’ is determined by measuring Nc, the total charged particle multiplicity in the pseudorapidity range 0.85<η<3.8. For both systems Si + Al and Si + Pb, an increase in the proton rapidity distribution dN/dy at midrapidity and a corresponding decrease at higher rapidities are observed with increasing Nc. For Si+Pb, Boltzmann slope parameters TB increase significantly in the most central collisions. The measured distributions exhibit a centrality dependence even when σ/σgeo≲10%, where full overlap between the Si and Pb nuclei occurs in a simple geometric picture. The proton rapidity distribution dN/dy is presented for the symmetric system Si+Al over the entire rapididty interval. The total number of protons, which is the integral of this quantity over rapidity, varies with Nc. Results are compared with various model calculations, mostly using the hadronic cascade codes ARC and RQMD. No significant nuclear transparency is observed, indicating that large baryon and energy densities are produced in these collisions.

1 data table

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